Diastereoselective spiroannulation of phenolic derivatives: Effect of steric hindrance on the diastereoselectivity.

The objective of this study was to determine the effect, if any, that steric factors have on the oxidative spiroannulation of simple phenols bearing substituents that are increasing in size. Specifically, we wanted to determine whether or not the diastereoselectivity of the reaction would improve. To do so, the synthesis of five phenols was carried out from which four of the five spiroether targets were synthesized. Based on the [superscript]1H-NMR of these four compounds, it was found that the diastereoselectivity in these reactions did not improve it actually decreased. The fact that the diastereomeric ratios did not improve with increasing steric factors provides evidence that the spiroannulation is not affected by the size of the group attached to the 3-position. Instead, it gives supporting evidence that the stereoelectronic effect and location of the substituent has greater effect to the overall outcome of the reaction. --P.ii.